An ongoing trend within telecommunications is the convergence of fixed and mobile networks, which is known as Fixed Mobile Convergence (FMC). The trend of evolving networks using IP-based technologies is common for fixed and mobile networks, which makes the convergence easier. By FMC, mobile and fixed network operators will be able to utilize their network resource more efficiently, which leads to reduction of capital and operational expenditure (CAPEX and OPEX). For instance, when a user is running an IP-based application such as Multimedia Telephony (MMTel) inside their home, it is more efficient to utilize broadband connectivity of the fixed access network rather than the wireless access network.
Residential networks are a key to the success of FMC because they are the most commonly used fixed network access by ordinary users. Therefore, it is important to be able to connect mobile phones to the Evolved Packet Core (EPC; see “Architecture enhancements for non-3GPP Accesses,” 3GPP TS 23.402, V8.2.0, 2008-06) through a residential network. Hereinafter the term User Equipment (UE) will be used in place of the term mobile terminal or mobile phone; the term UE is familiar in the 3rd Generation Partnership Project (3GPP) documentation.
3GPP defines mobile 2G/3G/LTE accesses and “non-3GPP accesses” (TS 23.402). The latter can be a fixed network. Many UEs address the FMC trend by providing multiple radio interfaces: one interface to connect to a 2G/3G/LTE access and a WiFi interface to connect to a fixed network.
TS 23.402 defines different ways for a UE to connect to the 3GPP core network (EPC) via a non-3GPP access network. These interfaces use either the Proxy Mobile IP (PMIP) or the Client Mobile IP (CMIP) mobility protocol. In this document, the use of CMIP is generally assumed; i.e. the interface known as S2c. 
The present applicant has appreciated the following technical issues with the situation as presently specified.
For advanced use cases, e.g. making an IMS voice call, QoS setup is required both in the EPC and in the non-3GPP access. How to do this for S2c is defined in TS 23.402. Following those definitions implies that the border gateway (BGW) in the non-3GPP access domain is required to setup a gateway control session towards the policy server in the EPC (the Policy and Charging Rules Function or PCRF). This gateway session is then used to download QoS rules. Downloading of rules is done upon attach, but possibly also at a later stage—e.g. when a user initiates a new session towards an application. Since gateway control sessions are by definition established on a per-user basis, the BGW is required to have the identification of the UE. The only secure way to acquire this identification is by involving authentication. Therefore, the specifications define 3GPP access authentication (i.e. user authentication in the access).
3GPP access authentication is only defined on a high level. When applying 3GPP access authentication in specific cases, e.g. when the non-3GPP access network is a BBF network (BBF stands for Broad Band Forum, the standardization organization for the fixed access; see http://www.broadband-forum.org/), the specifications do not promote a specific authentication protocol. Several candidates have been investigated, but the usefulness of these candidates depends very much on the specific network topology. Examples are: does the user configure its own WiFi AP (access point), or is this remotely managed by the operator? Is the residential gateway (RGW) bridged or routed? Is there a Network Address Translation (NAT) in the RGW?
It is desirable to address the above issues identified by the applicant.